Telephone



(No Model.)

Patented Apr. 5, 1892.

R B T WM Sm. E

A R OT B w H BL E T UNIT I ATENT OFFICE.

EDWARD G. ACHESON, OF PITTSBURG, PENNSYLVANIA.

TELEPHONE-TRANSMITTER.

SPECIFICATION forming part of Letters Patent No.472,243, dated April 5,1892.

Application filed June 29, 1887.

To all whom it may concern;-

Be it known that I, EDWARD G. ACHESON, a citizen of the United States,and a resident of Pittsburg, in the-county of Allegheny and State ofPennsylvania, have invented certain new and useful ImprovementsinTelephone- Transmitters, of which the following is a specification.

My invention relates to'telephone-transmitters; and it has for itsobject to improve the construction and arrangement of such instruments,so that they will be simple, cheap, and effective, less liable to getout of order, selfadjusting, and sensitive to very slight sounds; and myinvention consists in a telephonetransmitter constructed substantiallyas hereinafter described.

Referring to the accompanying drawings, Figure 1 is a diagrammatic viewshowing the essential features of my telephone and the manner ofconnecting the circuits. Fig. 2 is a similar diagrammatic illustrationshowing the arrangement of contacts upon the plate and electricalconnections therewith. Fig. 3 is a transverse section showing the mannerof supporting and adjusting the electrodes. Fig. 4 is a viewillustrating a modified form. Fig. 5 is a detail.

In carrying out my invention I make use ofa plate 1 of any suitablematerial, whether of metal, glass, wood, or equivalent, and in anydesired shape, whether round, square, or otherwise, and this plate isfreely suspended in any suitable manner, as by the cords 2, extendingfrom a support 3 and secured to the edges of the plate at 4. The plateis therefore free to vibrate bodily under the impact of sound-waves.Upon this plate, preferably at or near the center thereof, is mounted anumber of small blocks or buttons 5, of carbon or similar material, andif the plate is of conducting material these blocks, of course, aresuitably insulated from the plate. Two or more of these blocks arepreferably mounted upon each side of the plate, as shown in Figs. 2 and3.

Resting upon each pair of blocks'o is a bar 6 of carbon or othermaterial, and these bars are suspended by means of cords or threads 7,Which are secured to the plate at some convenient point, as at 8, sothat the bars rest by gravity upon the blocks.

Serial No. 242,883. (No model.)

While I have found in some instances that it is not necessary to providemeans for adj usting the pressure between the bars and blocks other thanthat caused by gravity, I prefer to provide some adjusting devicewhereby the initial contact between the bars and blocks maybe adjustedand their contact maintained. Thus in Fig. 1 I have'shown a spring orstrip of rubber 9, one end of which is secured to the plate, as at 10,andthe other end of which is preferably connected to an adj usting-wire11, which Wire-is secured to the plate, and by this means it will bereadily seen that the strip may be adjusted so as to cause the bars tobear with the desired pressure upon the blocks.

In Fig. 3 I have shown the bars 6 as provided with smaller rubber bands12, as seen in plan view in Fig. 5, and these bands are connected by athread 13, which may be tied or otherwise secured to the bands and whichpasses through an opening in the plate 1. This thread serves to maintainthe bars in position on the blocks 5. Sometimes, however, I preferablysecure a separate string or thread to each band on each bar and pass thethreads through eyes 14, secured near the center of the plate, andsecure the ends of the thread to the plate, as at the point marked x,the threads being indicated in Fig. 3 by dotted lines. This is aconvenient way to hold the bars, as the threads can be adjusted morereadily than when they are connected directly through the diaphragm. Ifthe telephone is subjected to loud sounds which cause severe vibrationsin the plate, I have found it desirable to provide additional elasticthreads 9, which pass over the outside of the bars and tend to rraintainthem in contact with the blocks; but under ordinary circumstances theselast adjusting-threads are not necessary.

In Fig. 4 I have shown another form of plate which I have foundconvenient to use and which consists of a plaque or dish-shaped plate ofany suitable material, the blocks 5 being secured, as before described,at or near the center of the plate. In this form I have shown balls orspheres 6, of carbon or other suitable material, suspended by thethreads 7 from the plaque. The plaque itself is also suspended in amanner similar to that shown in Fig. 1, so as to be free to vibrate, andin some instances I have found it desirable, especially when the plaqueis of light material, to attach to the bottom portion thereof a weight20, which serves to give it more steadiness in vibrating and render itless subject to disturbing air-currents.

The electrodes are included in two primary circuits or two branches ofthe primary of the induction-coil 15,0ne of the primary circuits, as 16,including the bar and blocks on one side of the plate and the otherprimary 17 including the bar and blocks upon the other side of theplate. These two primaries are wound in the coil 15 about the singlesecondary wire 18, so that the said secondary is influenced equally byeach of the primary circuits. These primary circuits are wound in such adirection that the currents passing through them normally counteracteach other in their effect upon the core of the secondary coil 15,tending to hold it in a neutral state. \Vhen the suspended plate isvibrated under the influence of sound-waves, the contact-pressurebetween the blocks and bar upon one side of the plate is caused toincrease, allowing more current to flow through the primary circuitconnected with such electrodes, and at the same time thecontact-pressure between the blocks and bar upon the other side of theplate is decreased, so that less current flows through the primaryconnected therewith, while the amount of current from the battery ispractically constant, the increase through one primary being balanced bythe decrease through the other. The variation of current flowing througheach of the primaries tends in the usual manner to produce an inducedcurrent in the secondary or line wire 18, and as the coils are wound, asbefore set forth, the effects of these opposite variations in thecontact-pressure between the sets of electrodes carried by the plate areunited and tend to induce a current in the same direction in thesecondary, so that practically double the effect of the variation in thecurrents in the primary of one set of electrodes is produced in saidsecondary. In this way comparatively slight variations in the contactbetween the electrodes will produce increased variation in the currentfiowiugthrough the secondary, and I am enabled, therefore, to producebetter effects from very slight disturbances of the contacts. It will beseen that by this arrangement the primary circuit is constantly closed,even when there is extreme disturbance of the plate from forcibleair-vibrations upon the same, for even if one set of contacts isseparated under the impact of sound-waves the other set must remain incontact and the danger from sparking and consequent burning of theelectrode is avoided, as the current always finds one passage openthrough which it can flow under all circumstances. By the use of thefreelysuspended plate I have found that comparatively large plates maybe used, so that very.

slight variations in the air-vibrations will effect the same, and I amtherefore enabled to transmit accurately both very feeble as well asstrong tones.

It will be seen that the above construction is exceedingly cheap andsimple and that no inclosing case is required, it being only necessaryto suspend the plate in any convenient position within reach of theair-waves produced by the person speaking, and the operati ve parts ofthe telephone being exposed, if any adjustment is required it can bemade without ditiiculty.

It will also be evident to those skilled in the art that certainfeatures of my invention may be used separately and in the combinationshown, as well as in other combinations of equivalent devices.

Having thus described my invention, what I claim is-- 1. In a telephone,the combination of a plate, blocks of conducting material secured oneach side of said plate, bars of conducting material resting thereon,rings of rubber surrounding each bar, and a thread or cord connected tosaid rings and securing said bars in position upon the blocks,substantially as described.

2. In a telephone, the combination of a suspended plate free to movebodily, blocks of conducting material secured to each side of saidplate, a bar of conducting material resting by gravity on each set ofblocks, and an elastic adj usting-eord passing over said bar,substantially as described.

3. The combination, with a plate, of blocks of conducting materialsecured on each side of the plate, a bar of conducting material restingon each set of blocks, and a thread or cord connecting said bars, thesaid thread being at. right angles to the plate, substantially asdescribed.

In testimon y whereof I have signed my name to this specification in thepresence of two subscribing witnesses.

EDWARD G. ACIIESON. Vitnesses:

F. L. FREEMAN, J. S. BARKER.

